Underwear, socks, undershirts, tights and leggings should be washed after every use, while bras, dresses, sweaters, skirts, pajamas and jeans can be washed after three to four wearings, as per American Cleaning Institute. Outerwear, blazers and casual jackets should be washed after 5-6 wearings, and shirts and t-shirts can be washed after one to two wearings.